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Merged Puzzling results from CERN

I am surprised the Vulcans haven't established first contact with us after the findings...
 
sol invictus said:
There must also be some uncertainty in when and where the neutrinos originate - presumably they're from the decay of some relativistic particle (muons perhaps) at LHC, which can't be pinpointed exactly.

But I suspect it's systematics in the distance measurement.
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It's pion decay. The problem is that they're ~100 GeV pions (speed of (1.0000001c) which decay in a 1000m flight tube. The time-difference between a pion transiting the whole tube, and a neutrino doing the same, is about 1.6 picoseconds.
 
Obviously the science ain't settled which is a good thing.
So when do they start raising the finance and building the super super dooper wazzit to see where they went wrong ?
 
temporalillusion said:
I'm pretty sure I've read of GPS accuracy down to the cm level for surveying type equipment.

http://en.wikipedia.org/wiki/Surveying#Surveying_equipment
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You are correct. And with additional equipment that isn't available to most surveyors, but some government agencies and research institutions, you can refine those measurements to even a fraction of a cm. :) I worked on a project for the USMC where we had to be to sub cm measurements. Cool toys!

ETA: And this wasn't differential GPS. ;)
 
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I can't post the link, but I found a paper where it says that a 1-2 cm accuracy with GPS is possible:

"A study by the Bundesamt fur Landestopographie in Switzerland [9] shows that accuracy of the order of 1 to 2 cm is possible, by using the international Global Positioning System (GPS). For instance, this can be achieved for Gran Sasso by using a total of 15 points (each with a pillar and a GPS antenna adapter). Five 24-hour sessions can provide an accuracy of 10^8 or better."
 
sol invictus said:
There must also be some uncertainty in when and where the neutrinos originate - presumably they're from the decay of some relativistic particle (muons perhaps) at LHC, which can't be pinpointed exactly.
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Would it be feasible to set up an experiment in which the neutrino generator, and two neutrino detectors are all in line, thus eliminating this source of systematic error?
 
In other news, this may help prevent Italian scientists from being sent to jail in the future, as it would allow them to predict future events with greater accuracy :)
 
Some more details from USA Today -

CERN says a neutrino beam fired from a particle accelerator near Geneva to a lab 454 miles away in Italy traveled 60 nanoseconds faster than the speed of light. Scientists calculated the margin of error at just 10 nanoseconds, making the difference statistically significant. But given the enormous implications of the find, they still spent months checking and rechecking their results to make sure there was no flaws in the experiment.
 
ben m said:
It's pion decay. The problem is that they're ~100 GeV pions (speed of (1.0000001c) which decay in a 1000m flight tube. The time-difference between a pion transiting the whole tube, and a neutrino doing the same, is about 1.6 picoseconds.
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I wasn't worried about the time difference from the mass, but rather the spread of the pion bunch (both along the beam direction and transverse to it).
 
naisel said:
I can't post the link, but I found a paper where it says that a 1-2 cm accuracy with GPS is possible:

"A study by the Bundesamt fur Landestopographie in Switzerland [9] shows that accuracy of the order of 1 to 2 cm is possible, by using the international Global Positioning System (GPS). For instance, this can be achieved for Gran Sasso by using a total of 15 points (each with a pillar and a GPS antenna adapter). Five 24-hour sessions can provide an accuracy of 10^8 or better."
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1cm is certainly good enough. I'm not sure I understand how they achieve that - where exactly are these pillars, and why can they receive the GPS signal under so much rock?

Another problem is the size of the neutrino detector, and how accurate it is at determining when and where the neutrino interacted inside it.
 
I'm with Sol. I doubt they have the exact distance measurement.

I'm also not even sure how much of an "exact" distance measurement you can get at that great of a distance on (in) the earth.
 
sol invictus said:
1cm is certainly good enough. I'm not sure I understand how they achieve that - where exactly are these pillars, and why can they receive the GPS signal under so much rock?

Another problem is the size of the neutrino detector, and how accurate it is at determining when and where the neutrino interacted inside it.
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I hope they aren't using "normal" GPS units that AFAIK are programmed to average out very small errors.
 
One method of using GPS to work out where you are deep underground is to work out where the spot is that is directly above you on the surface. Then work out that position using GPS.
To do the former they would have a lift that would go straight up. They know where the lift is both on the ground and at the level of the detector. They would be able to work things out from there. The actual method used may be different but this shows that there are solutions.
 
sol invictus said:
That's all I could think of too - but inside a mountain?

And they say a few billionths of a second, so for five sigma they need .5m accuracy or better. That's pushing the limits of GPS (might be beyond them, I'm not sure) even apart from the fact that they're under a lot of rock. Considering that earth tides can be a few cm, not to mention earthquakes, thermal expansion, etc., it sounds very hard to me. And the detector itself is probably meters across, and there's also uncertainty in the size of the source.

Color me skeptical.
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I've read about gps units mounted on bridges that have an accuracy of < 0.5 cm, used to monitor the sway of the bridge.

They use 2 things to enhance regular gps. One is an additional signal sent from a fixed ground station at a known position. The other involves looking at the phase of the gps signal instead of only looking at the time information encoded in the signal.
 
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rjh01 said:
One method of using GPS to work out where you are deep underground is to work out where the spot is that is directly above you on the surface. Then work out that position using GPS.
To do the former they would have a lift that would go straight up. They know where the lift is both on the ground and at the level of the detector. They would be able to work things out from there. The actual method used may be different but this shows that there are solutions.
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Sure - they can run an antennae up to the surface. But they need the precise position of the detector, not that of the corresponding location on the surface - so any procedure like that will inevitably introduce errors.

Molinaro said:
I've read about gps units mounted on bridges that have an accuracy of < 0.5 cm.

They used 2 things to enhance regular gps. One is an additional signal sent from a fixed ground station at a known position. The other involves looking at the phase of the gps signal instead of only looking at the time information encoded in the signal.
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I thought GPS always worked by phase. Isn't that why you need at least four (instead of three) satellites in view at any one time?
 
From Science: http://news.sciencemag.org/sciencenow/2011/09/neutrinos-travel-faster-than-lig.html?ref=hp

Jung, who is spokesperson for a similar experiment in Japan called T2K, says the tricky part is accurately measuring the time between when the neutrinos are born by slamming a burst of protons into a solid target and when they actually reach the detector. That timing relies on the global positioning system, and the GPS measurements can have uncertainties of tens of nanoseconds. "I would be very interested in how they got a 10-nanosecond uncertainty, because from the systematics of GPS and the electronics, I think that's a very hard number to get."
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sol invictus said:
I thought GPS always worked by phase. Isn't that why you need at least four (instead of three) satellites in view at any one time?
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The wiki entry for GPS has a section on accuracy enhancements. The one I remembered reading about with respect to the bridge monitors is called Carrier-Phase Enhancement.
 
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